XWIKI-17145: Add support for editing in-place the wiki pages for which the...

XWIKI-17145: Add support for editing in-place the wiki pages for which the default edit mode is WYSIWYG
* Fix a typo and improve the wording of the message displayed when a wiki page is locked because is part of an extension
* Extract the code from edit.vm that checks if an edit confirmation is needed into a Velocity macro that can be reused for in-place editing
* Small improvement of the edit confirmation displayed when the page is locked or protected (use button style and show avatar of locking user)
* Extract the code from edit.vm that determines the default document editor into a Velocity macro that can be reused for in-place editing